The present invention relates to a manufacturing technique of a semiconductor integrated circuit device and, more particularly, to a technique effectively applied to an exposure technique in a manufacturing process of the semiconductor integrated circuit device.
An extremely fine pattern of a solid element such as large-scale semiconductor integrated circuit or the like is formed by using chiefly a reduction projection exposure method that is one of optical lithography methods. This method is a method of reducing and transferring a mask pattern formed by a photomask or a reticle (called a mask hereinafter), onto a substrate by use of an imaging optical system.
Improvement of resolution in the reduction projection exposure method is advanced by high numerical aperture in the imaging optical system and short wavelength of exposed light. However, since there are needs of more extreme fineness for least process size of the solid element than the above-mentioned improvement, a deformed illumination exposure method or a phase shift mask exposure method, so-called a super resolution exposure method is developed and applied.
The phase shift mask exposure method includes, for example, a Levenson type phase shift mask, a halftone type phase shift mask, an auxiliary pattern arrangement type phase shift mask, and the like. The Levenson type phase shift mask is a mask generating a phase difference of 180 degrees between light beams that permeate regions between adjacent apertures (light permeating region) on the mask. The Levenson type phase shift mask also has an effect on further improvement of the resolution thereof within regions in which pattern-arranged pitches are extremely fine. For example, if a Levenson type phase shift mask is used, a reduction projection exposure method using KrF excimer laser light can eminently improve resolving characteristics even within a size region less than a least process size whose sufficient resolution is difficult to obtain in the case of use of normal masks. Further, the halftone type phase shift mask is a mask in which a halftone film is formed on a mask substrate instead of a light shield film. The halftone film has functions of making exposed light beams be permeated some percents and of generating a phase difference of 180 degrees between exposed light beams permeating the halftone film and permeating apertures around which the halftone film is removed.
And, the auxiliary pattern arrangement type phase shift mask is a mask having such a size as not to resolve on a semiconductor wafer around a main aperture and arranging auxiliary patterns for generating a phase difference of 180 degrees between exposed light beams permeating the main aperture. The auxiliary pattern arrangement type phase shift mask can be used when mask patterns are not arranged densely. For example, in a mask pattern for transferring isolated hole patterns, there is a structure of arranging auxiliary patterns which have such a size as not to be transferred on the semiconductor wafer of a plane surface containing upper, lower, right and left side of the main aperture and which generate a shift difference of 180 degrees relative to exposed light beams permeating the main apertures. This results in improvement of a light intensity profile of the main aperture and enhancement the resolving characteristics. This method is described in Japanese Patent Laid-open No. 5-19446, which discloses a technique of disposing auxiliary patterns on an end of dense patterns and around isolated patterns in order to enhance resolution of the dense patterns end and the like. Further, for example, Japanese Patent Laid-open No. 6-123963 discloses a technique of disposing respective auxiliary patterns such that light beams permeating respective adjacent patterns do not interfere with one another, or a technique of disposing one auxiliary pattern relative to the main aperture when the auxiliary patterns are arranged between the adjacent patterns. And, for example, Japanese Patent Laid-open No. 6-289591 discloses a technique of disposing auxiliary patterns in a symmetrically shifted manner in order to enhance flexibility in arrangement of the main apertures. Further, for example, Japanese Patent Laid-open No. 8-297359 discloses a technique of making layouts of mask patterns such that one main aperture and one auxiliary pattern are handled as one unit in order to facilitate the layouts of the mask patterns. And, for example, Japanese Patent Laid-open No. 11-84625 discloses a structure of disposing main apertures, auxiliary patterns, and shifters arranged like zigzag at dense main apertures, and of arranging the auxiliary patterns at each end of memory mats.
However, the present inventors have found that the above optical lithography technique has the following problems.
That is, although a technique of the Levenson type phase shift mask as described above is effective to enhance the resolution of extremely fine pattern being dense, phase shifters must be disposed such that each of phase difference of light beams permeating respective main apertures adjacent to one another is 180 degrees. Therefore, there occurs the problem that the phase shifters can not be disposed appropriately owing to arrangement of the mask patterns.
In the technique of the auxiliary pattern arrangement type phase shift mask, if auxiliary shifter patterns are arranged in an upper, lower, left or right directions, or in an oblique direction of 45 degrees of the main aperture, light beams permeating the adjacent auxiliary patterns interfere with each other, so that there is the problem that the auxiliary patterns can not be disposed appropriately.
That is, as fine patterns becomes high dense, it is difficult to merely dispose the phase shifters and auxiliary patterns. Therefore, there is the problem that when the patterns are transferred, sufficient tolerance of process thereof can not be ensured, transfer characteristic badness such as pattern-shape badness, and size-precision deterioration, and the like are brought, and fineness and high density of the patterns are impaired.
An object of the present invention is to provide a technique capable of transferring a semiconductor integrated circuit pattern disposed densely with sufficient process tolerance.
And, an object of the invention is to provide a technique capable of enhancing the transfer characteristics of the semiconductor integrated circuit pattern.
And, an object of the invention is to provide a technique capable of achieving fineness and high density of the semiconductor integrated circuit pattern.
The above and other object and new features of the present invention will be apparent from the description of the specification and the accompanying drawings.
Of the inventions disclosed in the present application, outlines of typical inventions are briefly described as follows:
That is, in the present invention, dense patterns are divided into a plurality of mask patterns capable of disposing phase shifters, and a predetermined pattern is transferred onto a semiconductor substrate by multiple-exposure thereof.
Further, the present invention has: a step of depositing a positive type photoresist film on a semiconductor substrate; a first exposure step of exposing a first mask pattern on said positive type photoresist film; a second exposure step of exposing a second mask pattern on said positive type photoresist film so as to be superposed on said first mask pattern; a step of performing development treatment relative to said positive type photoresist film after said first and second exposure steps and thereby forming a photoresist pattern formed of a positive type photoresist film on said semiconductor substrate; and a step of performing etching treatment relative to said semiconductor substrate by using said photoresist pattern as a mask and thereby transferring a predetermined pattern on said semiconductor substrate, wherein said first mask pattern has: a pattern for transferring a line pattern; and wherein the second mask pattern has a plurality of main light transferring patterns for separating said line pattern; a plurality of auxiliary light transferring patterns disposed such that distances between each of said main light transferring patterns and each of the auxiliary light transferring patterns thereabout the same and formed at such a dimension as not to be transferred on said positive type photoresist film; and a phase shifter disposed in any one of the main light transferring patterns and the auxiliary light transferring patterns and generating a phase difference in each transmission light.
Additionally, the invention has: a step of depositing a positive type photoresist film on a semiconductor substrate; a first exposure step of exposing a first mask pattern on said positive type photoresist film; a second exposure step of exposing a second mask pattern on said positive type photoresist film so as to be superposed on said first mask pattern; a step of performing development treatment relative to said positive type photoresist film after said first and second exposure steps and thereby forming a photoresist pattern formed of a positive type photoresist film on said semiconductor substrate; and a step of performing etching treatment relative to said semiconductor substrate by using said photoresist pattern as a mask and thereby transferring a predetermined pattern on an insulative film of said semiconductor substrate, wherein said first mask pattern has a pattern for transferring a first hole pattern of said hole pattern; and wherein said second mask pattern has: a plurality of main light transferring patterns for transferring a second hole pattern of said hole pattern; a plurality of auxiliary light transferring patterns disposed such that a distance between each of said main light transferring patterns and each of the auxiliary light transferring patterns is the same thereabout and formed at such a dimension as not to be transferred on said positive type photoresist film; and a phase shifter disposed in any one of said main light transferring pattern and auxiliary light transferring pattern and generating a phase difference in each transferring light.